With continuous improvement in the level of industrial development, application fields of light sources become increasingly diversified. For example, the light sources may be applied in image projection of rear-projection televisions or projectors, or used as illumination lamps for vehicles, vessels, or aircraft. Different application fields have different requirements on the color (or wavelength) of a light source. Currently, an excitation light source (having excitation light with a pre-determined wavelength) is used to illuminate a wavelength conversion device to excite the wavelength conversion material in the wavelength conversion device, thus obtaining light with a designated color (or wavelength). Common excitation light sources include traditional high pressure mercury light sources, and emerging semiconductor light sources (LED light sources) and solid-state laser sources. Among them, the brightness of the semiconductor light sources is insufficient, making it difficult for the semiconductor light sources to replace the traditional high pressure mercury light sources. Due to high brightness and high stability, the solid-state laser sources are gradually developed to be one of the main techniques among all excitation light sources.
FIG. 1 illustrates a schematic view of a structure of an existing wavelength conversion device. As shown in FIG. 1, the existing wavelength conversion device includes a wavelength conversion material layer 10′, a light-filtering layer 30′, and a dielectric layer 20′. In particular, the wavelength conversion material layer 10′ is configured on one side of an excitation light source, the light-filtering layer 30′ is disposed on one side of the wavelength conversion material layer 10′ facing towards the excitation light source, and the dielectric layer 20′ is sandwiched between the wavelength conversion material layer 10′ and the light-filtering layer 30′.
An operation process of the above-described wavelength conversion device is as follows. Excitation light emitted by the excitation light source traverses the light-filtering layer to illuminate the wavelength conversion material layer and excite the wavelength conversion material layer to generate excited light; a part of the excited light traverses the wavelength conversion material layer and emitted there-out, and the rest of the excited light as well as the excitation light unabsorbed by the wavelength conversion material are scattered to the light-filtering layer by the diffuse reflection effect and are further reflected back to the wavelength conversion material layer via the light-filtering layer. Accordingly, the rest of the excited light and the excitation light unabsorbed by the wavelength conversion material can be secondarily utilized, thus improving the utilization rate of the excitation light and the excited light. Particularly, the dielectric layer has a relatively low refractivity and can utilize all reflection to reflect large-angle light (including unabsorbed excitation light unabsorbed) from the wavelength conversion material layer back to the wavelength conversion material layer. Accordingly, excitation light unabsorbed by the wavelength conversion material layer can be secondarily utilized, thus further improving the conversion efficiency of the wavelength conversion device.
In the above-described wavelength conversion device, secondary utilization of the excitation light by the wavelength conversion material layer may increase the heat generated by the wavelength conversion material layer. However, thermal conductivity of the dielectric layer and the light-filtering layer are very poor, thus the heat of the wavelength conversion material layer is hard to be conducted out in time, and therefore the brightness of the excited light generated by the wavelength conversion device and the stability of the wavelength conversion material layer are reduced correspondingly. As the power of the excitation light increases, the heat generated by the wavelength conversion material layer increases, making it more difficult for the heat generated by the wavelength conversion material layer to be timely conducted out, thus rendering the reduction in conversion efficiency of the wavelength conversion device. Towards the above-described issues, there are no effective solutions so far.